Improvement in wood-screws



UNITED STATES PATENT OFFICE.

STEPHEN P. BURDIGK, OF NEW YORK, N. Y.

IMPROVEMENT IN1 WOOD-SCREWS.

Specification forming part of Letters Patent No. 137,4l4, dated April l, 1873; application led February 26, 1873.

To all whom it may concern:

Be it known that I, STEPHEN P. BURDIGK, of the city, county, and State of New York, have invented a new and useful Improvement in Screws; and I do hereby declare the following to be a full, clear, and exact description thereof, which will enable those skilled in the art to make and use the same, reference being had to the accompanying drawing forming a part of :this specification, in which drawing- Figure l represents a side view of my invention. Fig 2 is a section of the same in a larger scale than the previous figure; and Fig. 3 is a plan of a piece of timber, showing the opening produced by my screw. Fig. 4 is zltn efllge view of the harpoon-point shown in Similar letters of reference indicate corresponding' parts.

This invention consists in a screw with a thread composed ot' two members combined so that the outline of each thread presents the shape of an ovolo, and thereby a screw is obtained which can be driven home in wood without tearing the tbers, and which, when driven home, is firmly retained by the fibers catching in the recesses and against the shoulders of the succeeding threads so that the same can only be withdrawn by turning it in the proper direction. rEhe point of my screw is harpoonshaped, so that the same on being driven into wood will cut the fibers, and that the free ends of said bers produced by the action of said harpoon-shaped point are enabled to spring into the recesses of the succeeding screwthread, thereby retaining the bolt iirmly in position.

In the drawing, the letter A designates my screw, each thread a of which consists of two members, b o, the outlines of which, when combined, have the shape of an ovolo. (Best seen in Fig. 2.)

The pivot d of my screw is harpoon-shaped so that the same on being driven down into a piece of timber will cut the fibers, as Ashown reassume their original position wed ge them-` selves into the recesses c and against the shoulders formed at the junction of the members 'c and b of the successive threads, and the screw cannot be drawn out except by turning it round in the proper direction.

The tlat surface of my harpoon-shaped point forms a lock, which prevents the screw from turning round spontaneously, and the shoul-A ders or side points e cot' said point form wedges which force the wood apart whenever sufficient power is applied to turn the screw, and thus my screw can be readily turned in or out without splitting the wood.

Above the points e e is formed a sunken or depressed neck, f, so that as the screw is forced into the wood the fibers ofthe same immediately crowd into said neck in an unbroken state, and the liber is thus prepared for the further passage of the ovolo screw-threads through or down into the wood.

What I claim as new, and desire to secure by Letters Patent, is-

l. A screw having ovolo screw-threads, as herein shown and described, for the purpose specified.

2. A screw having a harpoonpoint d e e, as shown, and ovolo screw-threads, as set forth.

3. A screw having the depressed or sunken neck f and harpoon-pont d e e, substantially as herein shown and described.

S. P. BURDIOK.

Witnesses W. HAUFF, E. F. KASTENHUBEE. 

